Lots of pics after a wash
Your white balance is off in the first set...way too hot. Instead of using AWB, fine tune it to something in the range of 2500-2800K and see what happens.
Also, did you shoot these in RAW? I didn't take the time to check to see if the exif was intact, but if you shoot in RAW you will have greater flexibility in editing your shots. DPP, the program that came with your camera will let you edit RAW files, and so will Photoshop CS3. You will just have to download the RAW converter from Adobe's website.
Stop the camera down a few stops for those tough parking lot night shots; I'm assuming you're using the 28-135 lens that came with the 40D as part of the kit? That lens' sweet spot is right between f/8 and f/11, so use those numbers on aperture priority on the camera (Av). You might even get the cool little stars to appear on the overhead lights. Depending on how dark it is you should be seeing shutter speeds somewhere in the range of 10 to 15 seconds, depending on ISO, which should be set to 100 or 200 to get the lowest possible amount of noise in your pictures.
Make sure you have a good tripod so you can get some nice clean shots too. Looks like you may already have that covered.
It's all about angles when you're taking car photos. You'll find the right spot and it will make the picture just pop compared to some shots you have been taking at different angles. VegasBoy has some clean shots up on this website, so search for some of his stuff to get some ideas. Creativity is your best friend in the car photo department.
PM me if you'd like some more info...hope I could help!
Also, did you shoot these in RAW? I didn't take the time to check to see if the exif was intact, but if you shoot in RAW you will have greater flexibility in editing your shots. DPP, the program that came with your camera will let you edit RAW files, and so will Photoshop CS3. You will just have to download the RAW converter from Adobe's website.
Stop the camera down a few stops for those tough parking lot night shots; I'm assuming you're using the 28-135 lens that came with the 40D as part of the kit? That lens' sweet spot is right between f/8 and f/11, so use those numbers on aperture priority on the camera (Av). You might even get the cool little stars to appear on the overhead lights. Depending on how dark it is you should be seeing shutter speeds somewhere in the range of 10 to 15 seconds, depending on ISO, which should be set to 100 or 200 to get the lowest possible amount of noise in your pictures.
Make sure you have a good tripod so you can get some nice clean shots too. Looks like you may already have that covered.
It's all about angles when you're taking car photos. You'll find the right spot and it will make the picture just pop compared to some shots you have been taking at different angles. VegasBoy has some clean shots up on this website, so search for some of his stuff to get some ideas. Creativity is your best friend in the car photo department.
PM me if you'd like some more info...hope I could help!
Thanks for the comments guys...and the advice too, expect lots of PMs from me Moose! 
To answer some ?'s
My mods: AMS 2.0, AMS Race Head, GSC S2's, AMS Twin VSR w/880's, AMS 37R, AMS Race IC, AMS Fuel System, Greddy Ti, BR Spec CDi, HFS-5 Alky, Shep Ultimate Trans, Shep Stage III TC, Tilton Carbon/Carbon, and a few odds and ends here and there.
and the kit is Ings
To answer some ?'s
My mods: AMS 2.0, AMS Race Head, GSC S2's, AMS Twin VSR w/880's, AMS 37R, AMS Race IC, AMS Fuel System, Greddy Ti, BR Spec CDi, HFS-5 Alky, Shep Ultimate Trans, Shep Stage III TC, Tilton Carbon/Carbon, and a few odds and ends here and there.
and the kit is Ings
